Such illumination systems are known per se. They are used, inter alia, as luminaires for general lighting purposes, for example, for office lighting, shop lighting or, for example, shop window lighting. Alternatively, these illumination systems are used for lighting (transparent or semi-transparent) plates of glass or (transparent) glass or synthetic resin plates on which, for example, jewelry is displayed. These illumination systems are also used for advertising boards illuminating, for example, a partially transparent image from the back of the image.
The known illumination systems may also be used as light sources in backlighting systems in (picture) display devices, for example, TV sets and monitors. Illumination systems of this type are particularly suitable for use as backlighting systems for non-emissive displays such as liquid crystal display devices, also denoted LCD panels, which are used in (portable) computers or (portable) telephones.
An illumination system of the type described above, used as a luminaire, is known from, for example, Japanese patent application JP 04-276181. The luminaire is arranged for indirect illumination via a reflector having a circular arc-shaped cross-section protruding upwards in the width direction and has a center projection gradually tapering downwards at the center section in the width direction. The luminaire comprises straight tube-type fluorescent lamps facing the reflecting surface of the reflector at both end sections in the width direction of the reflector housing with an opening. The known luminaire has the disadvantage that it has a relatively poor uniformity over its light-emitting window.